9.8 Auto-numbering of the primary key values

The primary key numbering functionality automatically generates the primary key value when the entity object is used to insert a record. Due to this functionality, even if the user does not specify the primary key value, a unique value is stored. Cosminexus JPA Provider provides the primary key numbering functionality.

How to generate the primary key value

There are four methods for generating the primary key values:

• TABLE

  In this method, you generate the primary key values by using a table to store the primary key values.

• SEQUENCE

  In this method, you use the database sequence objects to generate the primary key values. However, if HiRDB is used as the database, implement the same processing as that of TABLE with Cosminexus JPA Provider.

• IDENTITY

  In this method, you use the identity column of the database to generate the primary key values. However, with Cosminexus JPA Provider, the operations differ depending on the database type used.

  In HiRDB, you implement the same processing as that of TABLE.

  In Oracle, you implement the same processing as that of SEQUENCE.

• AUTO

  You choose the generation method suitable for the database used. With Cosminexus JPA Provider, choose TABLE for both HiRDB and Oracle.

Timing when the primary key values are numbered

In Cosminexus JPA Provider, the primary key values are numbered during the flush operation or when a transaction is committed.

Example of SEQUENCE as the primary key value generation method

The following is an example of using SEQUENCE as the generation method of the primary key values. In this example, a sequence object named EMP_SEQ is assumed to have been created beforehand.

@Entity
public class Employee {
...
    @SequenceGenerator(
        name="EMPLOYEE_GENERATOR",
        sequenceName="EMP_SEQ"
 
    )
    @Id
    @GeneratedValue(strategy=GenerationType.SEQUENCE,
 generator="EMPLOYEE_GENERATOR")
    @Column(name="EMPLOYEE_ID")
    public Integer getId() {
        return id;
    }
...
}

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